This paper presents a novel modular soft robot, which can finish moving forwards. This intelligent system mainly consists of four deformable rubber cells, two friction feet, the solenoid valves, an air pump and the control systems. The size of each spherical cell and the shape of the soft robot can be changed, according to the appropriate inflating and deflating orders of the spherical cells. With two friction feet sticking with the ground in turn, the soft robot can make a peristaltic motion. Based on the geometric feature of the robot, the coordinates of cells' centers can be obtained. In this paper, in order to finish the motion, nine inflating and deflating orders are presented. Last, we present an experiment on four spherical rubber cells to test the peristaltic motion of the modular soft robot. According to the experiment, in a period the distance of the soft robot moving forward is 14cm, which is close to the theoretical distance 15cm.